The present invention relates to a thin-film type electromagnetic transducer formed on a nonmagnetic substrate by a thin-film forming process, and a method of transferring signals from the electromagnetic transducer.
Various information-recording devices have recently been studied and developed, for the purpose of improvement. These devices include the so-called IC cards which are small in size and handy, but which possess a large memory capacity. Some of these IC cards are already commercially available. In general, an IC card is the same size as a conventional so-called credit card, which carries a magnetic stripe on its top surface. The IC card contains a semiconductor memory, as an information storage means, in place of the magnetic stripe. A plurality of terminals are arranged on the top surface of the IC card. These terminals are electrically connected to the semiconductor memory, whereby information can be read from or stored in the memory.
In order to read information from or store it in the semiconductor memory of the IC card, the card is inserted in an information-reading/writing apparatus designed for its exclusive use. In this apparatus, the terminals of the IC card are brought into contact with terminals of the apparatus, so that the memory of the card is electrically connected to the apparatus.
However, this type of IC card, with terminals thereon, has the following drawbacks:
If the terminals of the IC card come into contact with any substance, such as clothes or a curtain made of synthetic fibers, which is stored with a lot of static electricity, the semiconductor memory of the card is liable to be damaged by the static electricity. Moreover, the IC card terminals, which come into mechanical contact with the terminals in the information-reading/writing apparatus, may eventually become worn away, thus causing contact errors. If the top face of each terminal is made somewhat lower in level than the top surface of the IC card, during the manufacture of the card, contact errors can then be caused by dust which may collect in the depressions defined by the top faces of the terminals. Because they have terminals for the semiconductor memory, furthermore, the prior art IC cards cannot be used with the information-reading apparatuses which are adapted for use with conventional credit cards having a magnetic stripe thereon. Thus, use of the conventional IC cards requires development and manufacture of new or modified information-reading/writing apparatuses for their exclusive use. Accordingly, users must purchase information-reading/writing apparatus solely for IC cards which are different than the information-reading/writing apparatus used for the conventional so-called credit cards.
Japanese Patent Disclosure No. 60-176188 discloses an IC card which has been developed in order to eliminate the aforesaid drawbacks of the prior art IC cards. This IC card uses electromagnetic transducers in place of the terminals. The transducer includes a substantially U-shaped core, which extends in the thickness direction of the card. Magnetic flux generated from either end of the core, therefore, is subject to variations in magnetic intensity, in the thickness direction of the card, that is in the direction intersecting with the surface of the card. Meanwhile, the conventional information-reading apparatuses for credit cards are designed so as to read changes in the magnetic flux along the surface of the credit cards. Accordingly, even if the disclosed IC card can be loaded into these conventional apparatuses, changes in the intensity of the magnetic flux, generated from the electromagnetic transducer of the IC card, cannot easily be read by the conventional reading apparatuses. If the changes are magnified, however, they can easily be read by the conventional apparatuses. To attain this, a relatively high current must be supplied to an electric circuit in the IC card. Those batteries which can be contained in the IC card cannot be supplied with such a high current, as they are liable to be used up too soon, due to their relatively small electric capacity. Without the use of such batteries, however, the IC card must be provided, on its surface, with terminals for the supply of high current from an external power source, in which case, they are liable to be subject to the aforementioned problems.